A conventional microprocessor includes an arithmetic logical unit array having a plurality of data registers for storing data, a plurality of fixed instruction registers for storing machine code instructions, and an arithmetic logical unit. The arithmetic logical unit applies an operation in accordance with one of the machine code instructions to the data stored in the data registers.
Each operation corresponding to a machine code instruction usually has a typical energy profile when executed so that monitoring the energy consumption of the arithmetic logical unit may make it possible to derive a conclusion regarding the executed operations and thus regarding the machine code instructions which have been carried out and consecutively regarding the source code executed by the microprocessor and/or regarding the internal functionality of the microprocessor. Thus, the security of the microprocessor may be breached.